A broadband wireless access system according to a related art will be explained in general as follows. Unlike the conventional 2G or 3G mobile communication systems, an IEEE 802.16e system, for which international standardization of a broadband wireless access system is in progress, is not provided with a hierarchical structure for a home location register (HLR), a visitor location register (VLR), a mobile switching center (MSC), a base station controller (BSC), a radio network controller (RNC) and the like. However, the IEEE 802.16e system includes a mobile subscriber station (MSS) as a mobile terminal, a base station (BS) and an authentication service authorization (ASA) as an authentication managing server. Furthermore a common physical layer (PHY) and a medium access control (MAC) layer are defined between the base station and the mobile subscriber station.
A media independent handover (MIH) technology according to a related art will be explained as follows. An object of an IEEE 802.21 system, in progress for the international standardization of inter-heterogeneous-network media independent handover, is to enhance user convenience for mobile terminal devices by providing seamless handover and service continuity between heterogeneous networks. An MIH function, event trigger, command service and information service (IS) are defined as basic requirements of the IEEE 802.21 system.
A mobile subscriber station is a multi-node that supports at least one interface type, wherein an interface can be implemented in various types. Possible interface types include a wire-line type interface such as an IEEE 802.3-based Ethernet, wireless interface types based on IEEE 802.XX including IEEE 802.11, IEEE 802.15, IEEE 802.16 or the like, and interfaces defined by a cellular standardization organization such as 3GPP and 3GPP2, for example.
FIG. 1 is an exemplary diagram of a multi-mode mobile subscriber station. Referring to FIG. 1, a multi-mode mobile subscriber station includes a physical layer (PHY) per mode and a medium access control (MAC) layer per mode. Furthermore, an MIH layer lies below an IP layer.
Media independent handover (MIH) is defined between IEEE 802-series interfaces or between an IEEE 802-series interface and a non-IEEE 802-series interface, such as a 3GPP or 3GPP2 interface. Also, a mobility supporting protocol of an upper layer such as a Mobile IP and session initiation protocol (SIP) is supported for the seamless handover service.
FIG. 2 is a diagram of a network model for a broadband wireless access system. Referring to FIG. 2, the network model shown represents a logical structure model of the IEEE 802.16 network. A U-interface defines management and control on a radio interface. An M/R interface defines management (M) and radio control (R) between a base station and a mobile subscriber station by a network control and management system (NCMS). An information service for media independent handover (MIH) in a broadband wireless access system can be provided by the NCMS. Alternatively, the NCMS acquires information from an information service (IS) server and then provides the acquired information to the base station or the mobile subscriber station.
FIG. 3 is a diagram of an alternative network model for a broadband wireless access system. Referring to FIG. 3, a base station communicates with the NCMS using primitives or parameters, and not through an M/R interface.
FIG. 4 is a diagram of another network model for a broadband wireless access system. Referring to FIG. 4, a management service access point (Management SAP) preferably performs functions such as system configuration, monitoring statistics, notifications/triggers and the like.
A control service access point (Control SAP) preferably performs the following functions and may further include other functions. The Control SAP may perform a handover function such as a handover notification from a base station, an idle mode mobility management function such as an idle mode entry of a mobile subscriber station, a subscriber and session management function such as a session request creation of a mobile subscriber station, and a radio resource management function, for example.
FIG. 5 is a flowchart of a mobile station initializing procedure in a broadband wireless access system. Referring to FIG. 5, once power of a mobile subscriber station is turned on, the mobile subscriber station searches a downlink channel and acquires uplink/downlink synchronization with a base station (1). The mobile subscriber station adjusts uplink transmission parameters by ranging with the base station, and the base station allocates a basic management connection identifier (CID) and a primary management CID to the mobile subscriber station (2). The mobile subscriber station then negotiates for a basic capability with the base station (3). Afterward, authorization is carried out on the mobile subscriber station (4). The mobile subscriber station then performs a registration procedure to the base station, wherein the base station allocates a secondary management CID to the mobile subscriber station managed by an Internet protocol (IP) (5). Once an IP connection is created (6), a current date and time are set (7). A configuration file of the mobile subscriber station is then downloaded from a trivial file transfer protocol (TFTP) server (8), and a connection for a prepared service is created (9).
An event trigger for handover between heterogeneous networks is explained as follows. For fast handover, a network layer uses information from a link layer to re-establish a connection as soon as possible. A link layer event helps to estimate a user's movement and may help a mobile subscriber station and network prepare the handover in advance. A trigger for handover may begin with a physical layer (PHY) and a medium access control layer (MAC). An origin of this trigger may be a local stack or a remote stack.
FIG. 6 is a diagram of a trigger model. An event trigger provides a state of a current signal, a state change of another network and an estimated change. The event trigger also provides a change between a physical layer and a medium access control layer, and attribute changes of a specific network.
Event types can be classified into the following: (1) PHY layer event; (2) MAC layer event; (3) Management event; (4) L3 event; and (5) Application event
Basic trigger events are explained as follows. A “Link_Up” event occurs when a Layer 2 (L2) connection is established on a specific link interface and when Layer 3 (L3) packets can be transferred from a higher layer. In this case, it is decided that all Layer 2 configurations configuring the link are completed. Event origins are a Local MAC and a Remote MAC. Corresponding parameters are shown in Table 1.
TABLE 1NameTypeDescriptionEventSourceEVENT_LAYER_TYPEOrigin from which event is generatedEventDestinationEVENT_LAYER_TYPEDestination to which event shall be deliveredMacMobileTerminalMAC AddressMAC address of MSSMacOldAccessRouterMAC AddressMAC address of old access routerMacNewAccessRouterMAC AddressMAC address of new access routerNetworkIdentifierMedia SpecificNetwork Identifier usable in detecting change ofsubnetIP_Renewal_IndicatorIndicating necessity of changing temporary IPaddress.0: change unnecessary1: change necessary
A “Link Down” event occurs when an L2 connection is released on a specific interface and L3 packets can no longer be transferred. An event origin is a Local MAC. Corresponding parameters are shown in Table 2.
TABLE 2NameTypeDescriptionEventSourceEVENT_LAYER_TYPEOrigin from whichevent is generatedEventDestinationEVENT_LAYER_TYPEDestination to whichevent shall bedeliveredMacMobileTerminalMAC AddressMAC address ofMSSMacOldAccessRouterMAC AddressMAC address of oldaccess routerReasonCodeReason why link isreleased
A “Link Going Down” event occurs when it is estimated that an L2 connection is going to link down within a specific time. The “Link Going Down” event may be a signal for initializing a handover procedure. Event origins are a Local MAC and a Remote MAC. Corresponding parameters are shown in Table 3.
TABLE 3NameTypeDescriptionEventSourceEVENT_LAYER_TYPEOrigin from which event is generatedEventDestinationEVENT_LAYER_TYPEDestination to which event shall be deliveredMacMobileTerminalMAC AddressMAC address of MSSMacOldAccessRouterMAC AddressMAC address of old access routerMacNewAccessRouterMAC AddressMAC address of new access routerTimeIntervalTime in msecsEstimated time for Link_UpConfidenceLevel%Estimated level for Link_Down of link in a specifictimeUniqueEventIdentifierUsed in case that Event rollback occurs
A “Link Going Up” event occurs when it is estimated that an L2 connection is going to link up within a specific time. The “Link Going Up” event is used when a lengthy amount of time is needed to initialize a network. Event origins are a Local MAC and a Remote MAC. Corresponding parameters are shown in Table 4.
TABLE 4NameTypeDescriptionEventSourceEVENT_LAYER_TYPEOrigin from which event is generatedEventDestinationEVENT_LAYER_TYPEDestination to which event shall be deliveredMacMobileTerminalMAC AddressMAC address of MSSMacOldAccessRouterMAC AddressMAC address of old access routerMacNewAccessRouterMAC AddressMAC address of new access routerTimeIntervalTime in msecsEstimated time for Link_UpConfidenceLevel%Estimated level for Link_Up of link in a specific timeUniqueEventIdentifierUsed in case that Event rollback occurs
A “Link_Available” event indicates that a new specific link is usable or available. The “Link_Available” event indicates the possibility that a new base station or access point can provide better link quality than that of a current base station or access point accessed by a mobile subscriber station. Event origins are a Local MAC and a Remote MAC. Corresponding parameters are shown in Table 5.
TABLE 5NameTypeDescriptionEventSourceEVENT_LAYER_TYPEOrigin from which event is generatedEventDestinationEVENT_LAYER_TYPEDestination to which event shall be deliveredMacMobileTerminalMAC AddressMAC address of MSSMacOldAccessRouterMAC AddressMAC address of old access routerMacNewAccessRouterMAC AddressMAC address of new access routerIP_Renewal_IndicatorIndicating necessity of changing temporary IPaddress.0: change unnecessary1: change necessary
A “Clear_Oldlink_Connection” event is explained as follows. If a link connection of a new medium access control layer is created, a mobile subscriber station triggers the “Clear_Oldlink_Connection” event to release a link connection of an old medium access control layer. An event origin is an MIH. Corresponding parameters are shown in Table 6.
TABLE 6NameTypeDescriptionEventSourceEVENT_LAYER_TYPEOrigin from whichevent is generatedEventDestinationEVENT_LAYER_TYPEDestination to which event shall bedeliveredMacMobileTerminalMAC AddressMAC address of MSS
An information service for inter-heterogeneous-network handover is explained as follows. A media independent information service (MIIS) provides a similar frame network on a hierarchical heterogeneous network to facilitate discovery and selection of various kinds of present networks. Namely, the media independent information service (MIIS) provides detailed information about a network needed to search and select the network. The MIIS should be accessible from any of the various kinds of networks and include information elements such as link access parameter, security mechanism, neighbor map, location, provider information, other access information, and cost of link, for example.
FIG. 7 is a flowchart of a procedure for acquiring an information service according to a related art. Referring to FIG. 7, an MIH of a mobile subscriber station (MS) transfers an MIH_info.request message to its MAC to request an information service (S710). The MAC of the mobile subscriber station then transfers an information request frame to a base station (BS) (S720). A MAC of the base station delivers the information request from the mobile subscriber station to its MIH via an MIH_Info.indication message (S730). The MIH of the base station then delivers a retained media independent information service to the MAC layer via a MIH_Info.response message (S740). This enables the MAC of the base station to send an information response frame in response to the mobile subscriber station (S750). The MAC of the mobile subscriber station receives the information response frame and delivers contents of the received information service to its MIH via an MIH_Info.confirm message (S760).
However, when a currently operating multi-mode mobile subscriber station in a broadband wireless access system performs media independent handover to another interface network, as shown in the flowchart of FIG. 7, providing an information service to the multi-mode mobile subscriber station is problematic because a method for exchanging an information service between a base station and an information service (IS) server is not clearly defined. Moreover, MAC management messages for transmitting and receiving service request and response messages between a base station and a mobile subscriber station are not defined.
Accordingly, what is needed is an invention for transmitting and receiving an information service for media independent handover that resolves the problems of the related art.